Motor-driven system for steering a vehicle

ABSTRACT

A motor driven system for steering a vehicle is provided, the system including a steering control device and a steering device connected through a motorized device, the motorized device transmitting movement to the steering device, the movement having an amplitude different from the movement given to the control device by the driver. The change in amplitude is controlled by a control unit according to various parameters. In this way, the degree of movement of the steering control device is changed by the motorized device such that operators having diminished physical capacity are able to operate the steering control.

BACKGROUND OF THE INVENTION

The present invention relates to a motor-driven system for steering avehicle, characterized in that the steering control device (e.g.steering-wheel) and the steering device (e.g. steering-box) areconnected through a motorized device suitable to transmit to thesteering device a movement having an amplitude different from themovement given to the steering control device by the pilot, said changeof amplitude being variable according to various parameters.

When the vehicle is steered through the control device and the motorizeddevice is operating, said motorized device can amplify the movementtransmitted to the steering device with respect to the movement given tothe steering control device by the pilot. In this case, the work of thepilot, which gives on said control device a reaction comparable with theaction he would have given in the absence of the motorized device, issmaller than that which would have been otherwise required, and thesteering is facilitated, in particular in small radius manouvres.

Moreover, the motorized device, when properly controlled, can evenreduce the amplitude of the movement transmitted to the steering devicewith respect to the movement given to the steering control device by thepilot, thus reducing the effect on the steering device of the pilot'saction.

The applicant, on the basis of his knowledge of the state of the art,believes that no devices have been on sale, or subject-matter of patentapplications, which achieve the advantages of the subject-matter of thepresent invention.

A number of devices, even electrical ones, suitable to reduce thesteering work, known as power steerings, are characterized in that thesteering movement given by the pilot remains unchanged between the inletand the outlet, while the force or torque which the pilot applies on thecontrol device is amplified. To this purpose, in all known powersteerings the steering action is increased by means of an actuatorlocated between the vehicle frame and the steering device, regardless ofthe fact that the actuator is of the electrical or hydraulic type orother types. Electrical power steerings of this type have been patented,among the others, by the companies ADWEST ENGINEERING LTD. (WO 9212037,etc.), ALFRED TEVES GMBH (WO 9214640, WO 9212885, etc.), DR. ING. H.C.F.PORSCHE AG (EP 0447626, etc.), HONDA GIKEN KOGYO KABUSHIKI KAISHA (EP0590576, etc.), KOSHIO SEIKO CO. (EP 0611691, EP 0350817, EP 0460406, EP0572961, EP 0566168, EP 0556869, EP 0556870, EP 0554703, EP 0531870, EP0536590, EP 0535422, EP 0611691, EP 0599260, etc.), LUCAS INDUSTRIES (EP0403234, etc.), MAN NUTZFAHRZEUGE AG (EP 0580997, etc.), MITSUBISHIDENKI KABUSHIKI KAISHA (EP 0360469, EP 0360470, EP 0351087, EP 0361726,EP 0513941, EP 0567991, etc.), MITSUBISHI JIDOSHA KOGYO KABUSHIKI KAISHA(EP 0440365, etc.), NIPPONDENSO CO. (EP 0460582, etc.), REGIE NATIONALDES USINE RENAULT S.A. (EP 0478437, etc.), ROBERT BOSCH GMBH (EP0480159, EP 0501017, EP 0545034, EP 0525574, etc.), SEXTANT AVIONIQUE(EP 0522924, etc.), STEERING DEVELOPMENT LTD. (EP 0165758), TEXASINSTRUMENTS INCORPORATED (EP 0481568, etc.), THE RAYMOND CO. (EP0490673, EP 0596167, etc.), TOYOTA JIDOSHA KABUSHIKI KAISHA (EP 0531962,etc.), VALEO ELECTRONIQUE (EP 0461037, etc.), VALEO SYSTEMES D'ESSUYAGE(EP 0491601, etc.), VOLKSWAGEN AG (EP 0591653, etc.), ZF FRIEDRICHSHAFENAG (WO 9314966, WO 9312965, etc.).

On the contrary, in the system of the present invention the pilot'ssteering work is reduced not by amplifying the force applied along therotation but conversely by amplifying the angle of rotation along whichthe force must be applied. To this purpose, the steering column is notcontinuous, i.e. the connection between the control device and thesteering device is not direct as in any known steering system, be itpowered or not. The interposition of the motorized device between thecontrol device and the steering device makes possible the amplificationor reduction of the rotation, thus achieving a steering angle differentfrom the angle normally produced by the gearing-down built in thesteering system. However, it is possible to apply the present steeringsystem in series with a known power steering, thus combining theadvantages of both apparatuses.

GB-A-2275032 discloses a control appliance for a vehicle steering systemwherein the steering column is divided into an input shaft and an outputshaft with a motorized drive therebetween, in the form of a self-lockingelectric motor. However, this system is an automatic steering controlsystem aimed at satisfying the highest safety requirements whileavoiding as far as possible the irritation of the driver caused by itsautomatic intervention on the front steered wheels, said interventionbeing intended to compensate for particular driving conditions (e.g.side wind) detected by relevant sensors. Such a kind of operationimplies that the system acts only when the input signals from thesensors indicate that an automatic intervention is required, whiletrying to minimize the effect of the correction on the steering wheel.This is quite the opposite of the operation of the present system, whoseactivation can only be determined by the input coming from the driverthrough the movement of the steering wheel. Therefore, it is clear thatsuch an automatic control system is not designed to help the driver inhis steering action but rather to provide an autonomous steeering actionpossibly superimposed on the driver's one.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to help the pilot during thesteering of a vehicle by modifying properly the amplitude of themovement transmitted to the steering device with respect to the movementgiven to the control device.

Another object of the present invention is to control the action of thepilot on the steering device so as to prevent undesirable manouvres.

Another object of the present invention is to make easily the steeringcontrol remote.

Another object of the present invention is to achieve all of the abovewith a reliability of the steering system which, in case of failure ofthe motorized device and of the control unit thereof, is equal to thereliability of a mechanical system.

Another object of the present invention is to achieve all of the aboveon an existing vehicle provided with a conventional steering system,with minor changes to the structure and arrangement of the originalsteering devices.

Another object of the present invention is to achieve all of the aboveat a very low cost.

Thanks to the action of the motorized device, the pilot can achieve thesteering with an effort comparable to the effort he would have made inthe absence of said device, but with a lower amplitude of the movementof the control device. This allows to achieve the steering throughcontrol devices characterized by very small global movements, such asfor example devices in the form of a cloche, a handlebar or a joystick,yet retaining a precision in the steering control comparable with theprecision of conventional highly geared-down steering devices.

Therefore, the subject-matter of the present invention is particularlyuseful in all those steering manouvres which require large movements ofthe control device, such as the rotations of the steering-wheel duringparking manouvres or on tortuous roads. Furthermore, the subject-matterof the present invention is particularly useful for the purpose ofallowing the steering with conventional steering-wheels or helms topeople with little functional capacity of the upper limbs, such as, forexample, people affected by some myopathies, or without the use of onearm. In fact, these people may have sufficient strength in the hands andwrists to hold the steering-wheel, but not enough strength in theshoulders to move the arms enough for rotating the steering-wheel beyonda small arc of rotation.

Also, the possibility of properly changing the amplitude of the movementtransmitted by the control device to the steering device, while allowingin some situations the amplification of the pilot's action, in the sameway it allows in other situations to have a direct transmission or thereduction of the effect of the pilot's action.

In order to assure the reliability of the steering system even in caseof failure of the motorized device, it is sufficient to use anirreversible motorized device or to provide a simple locking devicesuitable to make mutually integral the two parts of the motorized devicerespectively coupled to the control device and the steering device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other objects, advantages and characteristics of the steeringsystem according to the present invention will be apparent to thoseskilled in the art from the following detailed description of somepreferred embodiments thereof, reported as non-limiting examples,referring to the annexed drawings wherein:

FIG. 1 schematically shows a first embodiment wherein the motorizeddevice is placed between the steering control device, in the form of asteering-wheel, and the steering device, in the form of a steering-box.

FIG. 2 schematically shows a second embodiment similar to the embodimentof FIG. 1, wherein the motorized device is provided with a lockingdevice suitable, in pre-established situations, to make mutuallyintegral the two parts of the motorized device respectively coupled tothe control device and the steering device.

FIG. 3 schematically shows a third embodiment similar to the embodimentof FIG. 2, provided with a sensor of the angular position of thesteering-wheel, a sensor of the angular position of the wheels and alocking device suitable to prevent the movement of the control device.

FIG. 4 schematically shows a fourth embodiment, wherein the motorizeddevice is placed inside the steering-box.

FIG. 5 schematically shows a fifth embodiment similar to the thirdembodiment of FIG. 3, wherein the control device is in the form of ahandlebar and the steering device transmits the movement to a controlrudder.

FIG. 6 schematically shows a sixth embodiment similar to the precedingembodiment of FIG. 4, wherein the control device is in the form of acloche and the motorized device is in the form of a linear actuatorwhich transmits the movement to a control rudder.

FIG. 7 shows a block diagram which illustrates the operation of thedevice shown in FIG. 1, assuming that the pilot directly controls themotorized device through a control unit.

FIG. 8 shows a block diagram which illustrates the operation of thedevices shown in FIGS. 3 to 6, assuming that the motorized device iscontrolled by a control unit according to the value of the quantitiesdetected by the position sensors.

FIG. 9 shows a block diagram similar to the preceding one, assuming thatthe motorized device is controlled by a control unit according to thevalue of the quantities detected by the position sensors and by othersensors. The diagram also includes the possibility that the steeringcontrol be made remote by transferring it to an additional joystick,mechanically separate from the kinematic chain which links the controldevice to the steering device.

FIG. 10 is a schematic longitudinal sectional view of a practicalembodiment of a reversible motorized device.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the subject-matter of the present inventionincludes a motorized device (2), which connects the steering controldevice (1), in the form of a steering-wheel, to the steering device (3),in the form of a steering-box, said motorized device (2) being of theirreversible motor-reducer type, i.e. such that the steering actionexerted by the pilot is directly transmitted to the steering-box (3)when the motorized device (2) is inactive. The motorized device (2) canbe activated by the pilot, e.g. through pushbuttons located on thesteering-wheel (1) or on the vehicle's frame. This simple operation ofthe system, of the open-loop type, is described in the correspondingblock diagram of FIG. 7. When the motorized device (2) is activatedthrough the control unit, it produces a movement, e.g. a rotation,through which it acts on the steering device (3), while the pilot exertsa simultaneous reaction on the steering-wheel (1). In this way, thesteerings or the turns with small turning radius--e.g. frequent inparking manouvres or city driving--can be achieved through smallmovements of the control device (1), thus achieving the above-mentionedadvantages.

In FIG. 2 there is shown an embodiment of the present invention which issimilar to the embodiment of FIG. 1, being different therefrom in thatthe motorized device (2), which is assumed reversible, is provided witha locking device (4) suitable to make integral the inlet and outlet ofthe motorized device (2), so that in particular situations--e.g.steering with small angles of rotation of the control device (1), or incase of failure of the motorized device (2)--the steering can beachieved by direct action of the pilot as it usually occurs in aconventional steering system.

In FIGS. 3 to 6, and in the corresponding diagrams of FIGS. 8 and 9,there are shown embodiments of the present invention which are similarto the preceding ones but also include at least one position sensor (5)placed upstream and possibly at least one position sensor (6) placeddownstream from the motorized device (2). For example, in a particularand non-limiting way of operation of the invention generally disclosedin the block diagram of FIG. 8, the motorized device (2) could beactivated only upon exceeding of a pre-established angle of rotation ofthe steering-wheel detected by sensor (5), or of a pre-establishedvelocity of rotation, or of both, according to pre-established modes.Therefore, the control unit can be programmed with different laws forgearing down and/or up the rotations of the steering-wheel, e.g. asquare law, an exponential law, etc. The effect of the motorized device(2) on the steering device (3) will be more or less high according tothe selected law and the amount of rotation, even allowing the pilot todrive without ever moving the hands on the steering-wheel.

In another application of the subject-matter of the present invention,the steering control unit could limit the pre-set steering amplificationratio according to signals coming from sensors of position, speed,acceleration, etc. (FIG. 9), i.e. according to the specific drivingconditions. This is particularly useful in the case of a pilot's actionnot adequate to the road holding conditions of the vehicle, whereby thissystem can act as an additional safety device to prevent about-faces,etc.

In another embodiment, the system of the present invention includes alocking device (7) suitable to prevent the movement of the controldevice (1), thus allowing the remote steering control. This function,generally disclosed in the lower row of the block diagram of FIG. 9, isparticularly useful for those which must simultaneously drive andoperate machines. Furthermore, it makes driving possible to people withlimb functionality insufficient for using a mechanical steering. Thelocking device (7) is required to provide the opposing reaction on thesteering-wheel when the pilot acts directly on the remote control (e.g.joystick).

In FIGS. 5 and 6 the system of the present invention is shown in anembodiment suitable to move a control rudder. In FIG. 5, the pilotcontrols the direction through a handlebar (1) keyed upstream from themotorized device (2); in FIG. 6 the handlebar is replaced by a cloche(1) acting with a favourable lever ratio on the motorized device (2)which is in the form of a linear actuator, and which provides theamplification of the movement of the mechanism placed between the cloche(1) and the control rudder (9).

In FIG. 10, there is shown a practical embodiment of the motorizeddevice (2) which includes a stepper motor (10), an electromagnetic brake(11) and an epicyclical reversible reduction gear (12). The position ofthe steering-wheel is detected by a first position sensor (13) locatedat the upstream end of the motorized device (2), while the position ofthe steering device is detected by a second position sensor (14) locatedat the downstream end. The first sensor (13) is in the form of arotating resolver connected to the shaft (15) of the steering-wheelthrough a cog belt (16). A reduced bulkiness is obtained through thesecond sensor (14), which is a linear transducer activated by a threadedflange (17) moved by a screw (18) secured onto the shaft (19) to thesteering device.

The electromagnetic brake (11) is connected so that in the absence ofthe power supply, i.e. inactive device or failure, it makes motor (10)integral with reduction gear (12) thus restoring the direct connectionbetween the steering-wheel and the steering device. The use of a steppermotor is desirable for its high torque features useful for smallmovements of high-inertia systems.

In case of use of a remote control (e.g. joystick), the steering-wheelis locked and the joystick is directly connected to the inlet of sensor(13) which will therefore detect the joystick position.

All these examples have the common feature that the subject-matter ofthe present invention changes only the amplitude of the movementtransmitted by the control device (1) to the steering device (3), withthe main object of achieving the steering through a pilot's movement ofsmaller amplitude, and consequently less work with respect to what wouldotherwise be required in the absence of said device.

It is pointed out that these examples have been illustrated with theonly aim of describing said operating principle of the motor-drivensteering system which is the subject-matter of the present invention,regardless of the embodiment of the steering control device (1), of themotorized device (2), of the steering device (3) and of the devices (8)or (9) which give the direction.

In fact, it can be easily understood that said motor-driven steeringsystem can be accomplished with motors or rotating/linear actuatorsoperating on any kind of energy: electric, hydraulic, pneumatic,thermochemical, etc., or it can be accomplished with steering mechanismsdifferent from the conventional steering-box of a motor vehicle, or withdirecting devices different from the wheels of a motor vehicle, or thecontrol rudder of a boat or aircraft, such as, for example, runners, ordevices for controlling an helicopter rotor, etc.

What is claimed is:
 1. A motor-driven system for steering a vehicle,including a steering control device (1) and a steering device (3)connected through a motorized device (2) for changing the ratio of thesteering angle transmitted between the steering control device (1) andthe steering device (3) and to restore a direct connection therebetweenin case of failure of the system, the operation of said motorized device(2) being controlled by a control unit, the motorized device (2) beingactivated only in response to the movement of the steering controldevice (1) and functioning in a manner which requires the operator toexert an opposite equivalent reaction on the steering control device(1).
 2. A motor-driven system for steering a vehicle, according to claim1, wherein the motorized device includes an irreversible motor-reducer.3. A motor-driven system for steering a vehicle, according to claim 1,characterized in that the motorized device (2) includes anelectromagnetic brake (11) connected so as to lock the inlet of saidmotorized device (2) to the outlet thereof in case of failure.
 4. Amotor-driven system for steering a vehicle, according to claim 1,characterized in that the motorized device (2) is controlled by aclosed-loop control system wherein the control unit is operativelyconnected to sensors (5) of the position of the steering control device(1) and/or to sensors (6) of the position of the steering device (3). 5.A motor-driven system for steering a vehicle, according to claim 4,characterized in that the control unit is further operatively connectedto sensors for detecting other parameters such as the vehicle speed, thevehicle acceleration components, etc.
 6. A motor-driven system forsteering a vehicle, according to claim 1, characterized in that themotorized device (2) is placed inside the steering device (3).
 7. Amotor-driven system for steering a vehicle, according to claim 1,characterized in that it further includes a locking device (7) suitableto prevent the movement of the steering control device (1) and toprovide the relevant reaction thereon, as well as a remote controldevice operatively connected to the control unit and suitable to act asa remote steering control device.
 8. A motor-driven system for steeringa vehicle, according to claim 3, characterized in that the motorizeddevice (2) includes an electric motor (10), an electromagnetic brake(11), an epicyclical reversible reduction gear (12), a first positionsensor (13) located at the upstream end and a second position sensor(14) located at the downstream end.
 9. A motor-driven system forsteering a vehicle, according to claim 8, characterized in that saidfirst and second sensors (13, 14) are rotating resolvers respectivelyconnected to the shaft (15) of the steering-wheel and to the shaft (19)of the steering device through cog belts (16).
 10. A motor-driven systemfor steering a vehicle, according to claim 8, characterized in that saidfirst and second sensors (13, 14) are linear transducers respectivelyconnected to the shaft (15) of the steering-wheel and to the shaft (19)of the steering device, and activated by a threaded flange (17) moved bya screw (18) secured onto said shafts (15, 19).